Graphene formed of a single layer including sp2-bonded carbon atoms aligned in a typical two-dimensional carbon nano material has attracted extensive attention due to its excellent electrical, mechanical and thermal properties. Not only graphene but also graphene oxide (GO) and reduced graphene oxide (rGO) as graphene derivatives have attracted a lot of attention from various research fields such as sensing, nanoelectronics, energy storage, catalyst, and nanobiotechnology, etc. In recent years, metalworking-processed rGO/composites or nanocompounds have attracted a lot of attention from the academic world due to their optical, electrotechnical, thermal, mechanical, and catalytic properties. The ultimate goal is to prepare compounds or composites by integrating polymers, metal nanoparticles (NP), or nanotubes and fullerene with GO or rGO. Due to a large surface area and the above-described properties, GO has become an attractive substitution as a matrix for nanocompounds.
However, so far, there have been few reports on the use of GO or rGO as a mold for directly synthesizing metal nanoparticles and directly preparing a metal nanoparticle-GO compound on a substrate. Metal nanoparticles are highly important due to their optical, catalytic, electrical, and antibiotic properties. Preparation of metal nanoparticles within a synthesis material has also attracted attention in order to increase their properties and applicability. Therefore, integration of GO or rGO with metal nanoparticles or synthesis of metal nanoparticles using GO or rGO as a mold is a major purpose of research. Muszynski et al. synthesized gold (Au) nanoparticles using chemical reduction of NaBH4 and HAuCl4. In this synthesis, a graphene-octadecylamine suspension in THF was used and metal borohydride was used as a reducing agent. However, such a process is not an environment-friendly process. Further, gold nanoparticles were just anchored on graphene functionalized with octadecylamine but not directly anchored on a surface of the graphene. Recently, Nanda et al. synthesized M@rGO using zinc and H2SO4. In this synthesis, powder of a metal (Zn) was used to prepare nanoparticles of another metal. A high concentration of H2SO4 (10 M) was needed to prepare small metal nanoparticles, and when a low concentration was used, large nanoparticles (50 nm) were obtained. However, in this method, a material which is not suitable to be used as a conductive material in a transparent conductive electrode was produced.
Further, conventionally, there was an attempt to perform electrical deposition in order to prepare a composite by integration of GO or rGO with metal nanoparticles. Korean Patent Laid-open Publication No. 10-2011-0110538 (published on Oct. 7, 2011, entitled “Nanostructured film on the graphene by electrochemistry”) may be one of examples.